This invention relates to a fixed hard disc drive assembly including a hermetically sealed housing having an air cleaning means disposed therein.
Hard disc storage media is extensively used with computer equipment for data storage and data handling applications, but when such high storage density discs are employed care must be taken to minimize dust and the like. In a hard disc drive assembly the read-write heads float on a thin layer of air very close to the disc surface during the read-write operations, and any particles on the surface of the disc will interfere with the spacing of the heads and prevent their proper operation. In many instances, dust particles or the like may lodge between the rapidly spinning disc surface and the associated read-write heads and cause the physical destruction of these delicate components. The hard discs and the associated read-write heads are thus usually enclosed within a hermetically sealed envelope or housing, and an air cleaning system is disposed within the housing to provide a cleansing air circulation over the disc surfaces.
A conventional fixed hard disc drive assembly having an air cleaning system is shown in FIG. 1, wherein a plurality of fixed hard discs 2 (only one is shown) are mounted on the rotor of a spindle motor 3 for counter clockwise rotation. Read-write heads 5 are disposed proximate the surface of the discs 2, mounted on coupled arms 51, 52 driven by an actuator (not shown) to accurately position the heads. The foregoing structure is enclosed within a hermetically sealed housing 1. An air filter assembly 4 is disposed at one end of the rectangular portion of the housing, with its intake side facing towards the air flow generated by the rotation of the discs. An internal baffle block 6 helps to channel the air toward the filter inlet.
When the spindle motor 3 and the hard discs 2 are driven at high velocities, air flows radially and circumferentially outwardly, in a spiralling manner, due to the pressure difference caused by the centrifugal pumping effect of the rotating discs. A layer of cleansing air thus flows over the surfaces of the discs. The centrifugal action gives a circumferential component of velocity to the air which forces it into the space 61 between the block 6 and the housing 1, and then into the intake of the air filter 4. The cleansed air exiting the filter travels as shown by the arrows 63 to return to the low pressure area at the center of the discs, thus establishing a continuous air flow cycle.
FIG. 2 shows another conventional fixed hard disc drive assembly, wherein the air filter 4 is disposed directly in the path of the air flow and the baffle block 6 shown in FIG. 1 is dispensed with.
FIGS. 3(a) and 3(b) show a further conventional disc drive assembly, wherein the intake side of the air filter 4 faces downwardly and an air guide or duct 7 is disposed between the outlet side of the filter and the center portion of the discs.
In these conventional arrangements the pressure difference between the intake and outlet of the air filter is relatively small, which results in a low filtration efficiency.